A precise and well-orchestrated set of molecular and cellular signals governs the differentiation and function of the luman placenta. Surfacing the placental villi, the trophoblast bilayer of the human placenta is well positioned to execute a series of functions that are essential for placental metabolism, and consequently facilitate fetal development. Whereas recent studies illuminated spatial and temporal pathways that influence transcriptional regulation of trophoblast genes in mouse, sheep and human placentas, little is known about the integration of these signals into maintenance of trophoblast tiomeostasis and placental adaptation to injury. Practically unknown five years ago, microRNAs (miRNAs) are ubiquitously expressed in tissues of diverse organisms, from worms to humans. As a part of the endogenous RNA silencing machinery, these short RNA strands act in concert with the RNA interference silencing complex to degrade target transcripts and silence translation, and thereby regulate development and maintain homeostasis. Moreover, dysregulated miRNA expression has been implicated in human diseases. We and others have recently shown that both the mouse and human placentas express miRNAs, yet their pattern of expression and function are unknown. Considering the fundamental role of the placenta in development of the mammalian embryo, as well as the profound consequences of placental dysfunction, it is paramount to investigate the function of miRNAs in this organ. This exploratory translational research project, which bridges recently discovered miRNA pathways to human trophoblast biology and disease, matches the R21 funding objectives. In the proposed work we will test the hypothesis that discrete miRNA species are expressed in human trophoblasts and regulate normal placental function as well as adaptive response to hypoxic injury. Information gleaned from our studies will likely shed light on novel mechanisms that govern trophoblast adaptive response to injury, and uncover the role of endogenous RNAi in the differentiation and function of the human placenta. [unreadable] [unreadable] [unreadable]